Neutron Depth Profiling Study on ⁶Lithium and ¹⁰Boron Contents of Nuclear Graphite

ABSTRACT

⁶Li and ¹⁰B contents in the nuclear graphite need to be calculated and evaluated for ⁴He and the gaseous nuclear radioactive waste ³H, which should be eliminated to an acceptable low level. Furthermore, it will help analyze the diffusion and adsorption behavior as precursors of ³H and ⁴He. Based on reactions of ⁶Li(n,α)³H and ¹⁰B(n,α)⁷Li, we employ Neutron Depth Profiling (NDP) as a non-invasive and versatile technique, providing ⁶Li and ¹⁰B content of three different kinds of nuclear graphite, including fuel element matrix graphite, reflector graphite, and boron-containing carbon bricks in High-temperature Gas Reactor (HTGR). The ⁶Li depth distributions and total amounts calculated from ⁴He and ³H are compared with high precision for evaluating gaseous radionuclides release. The calculated ¹⁰B content of boron-containing carbon bricks is needed for analyzing the impurity and neutron absorption capacity. We offer a new method to measure the trace content of isotopes along the depth of various nuclear materials, which is important for studying the reactor activation products and supporting the service and safety of reactors.

KEYWORDS:

• Nuclear graphite
• neutron characterization
• high-temperature gas reactor

Acknowledgments

The authors wish to thank the thermal neutron beamline NDP laboratory at the Reactor Institute Delft, Key Laboratory of Radiation Beam Technology and Material Modification (Ministry of Education), Beijing Normal University, and the central laboratory of the Institute of Materials Science and Engineering. The authors are grateful to the Natural Science Foundation of China (under Grant 11975135 and 12005017).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [11975135 and 12005017].